Organic dithiophosphates having a chloro-p-thioxane nucleus



ORGANIC DITHIOPHOSPHATES HAVmG A CHLORO-p-THOXANE NUCLEUS Albert H. Haubein, Christiana, DeL, assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 30, 1955, Serial No. 531,602

16 Claims. (Cl. 167-33) This invention relates to new and useful organic dithiophosphate compounds and to pesticidal compositions containing the same.

The novel organic dithiophosphate compounds of this invention have the general formula S 01 si (OR) 4-5 2 L n S in which each R represents a lower alkyl radical and n represents a number from 1 to 2.

These organic dithiophosphate compounds have pesticidal properties and distinguish themselves from known pestidicial compounds in being more toxic at low concentrations toward certain pests and in having a much longer residual toxicity toward mites when sprayed on plants normally attacked by such pests.

The organic dithiophosphate compounds of this invention are made by reacting tetrachlorothioxane with the desired diester of dithiophosphoric acid, the latter being the product of reaction of a lower aliphatic alcohol or a mixture of lower aliphatic alcohols of the formula ROH and P285. The diester of dithiophosphoric acid may be reacted directly with the tetrachlorothioxane or it may be reacted in the form of its salt or in the presence of materials which sequester the hydrogen halide set free in the reaction.

The methods of making the products of this invention and methods of using the products as pesticides are more particularly described in the following examples in which all parts and percentages are by weight.

Example 1 Tetrachlorothioxane was prepared by contacting thioxane in carbon tetrachloride solution with chlorine gas at about 5580 C. until a tetrachlorothioxane was produced. The efliciency was very close to 100%.

To a stirred solution of 16.0 parts pyridine and 0.2 part hydroquinone in 100 parts benzene was added over a 15- minute period 42.0 parts 0,0-diethyl dithiophosphoric acid. To the resulting salt solution was then added 24.0 parts tetrachlorothioxane prepared as above. The mixture was then held at 4080 C. for 5-6 hours during which time pyridine hydrochloride separated. At the end of this time, water was added to dissolve the water-soluble salts and the organic layer was further purified by washing first with 5% sodium hydroxide solution and then with water. After drying over sodium sulfate, the solvent benzene was removed under reduced pressure and the residue was topped at 85 C./0.5 mm. The residue, which was the bis(diethyl dithiophosphate) of dichlorothioxane dithiol, also designated dichlorothioxanedithiol- S,S-bis (0,0-diethylphosphorodithioate), amounted to 39 parts and had the following analysis: S, 27.4%; Cl, 14.6%; P, 10.1%; (calcd. for the designated ester: S, 29.6%; C1, 13.1%; and P, 11.4%).

An emulsifiable concentrate of the residue was made 2,766,169 Patented Get. 9, 1956 by mixing 1 gram of the residue with 1 ml. benzene and 1 ml. sorbitan monolaurate polyoxyalkylene derivative (Tween 20). This concentrate was then diluted with water to form dispersions of the residue in water varying in concentration from 1.0% to 0.01%. The dispersions were then tested for their toxicity to caged insects and to mites not only by spraying the insects but by spraying the plants alone as well as for the purpose of determining residual toxicity. Standard test methods were used for obtaining the results tabulated below.

Tests showed that a 0.025% emulsion of the composition of this example produced a kill of pea aphids when sprayed on pea plants infested with pea aphids.

Similar tests on residual activity to Mexican bean beetles with which lima bean seedlings treated at 0.1% concentration were infested showed 60% mortality in two days.

Tests as an insecticide against houseflies showed 96% kill using a 0.1% emulsion.

Tests against the two-spotted mite showed 100% kill with a 0.01% emulsion.

Example 2 Trichlorothioxanemonothiol S-(0,0-diethyl phosphorodithioate) was prepared from tetrachlorothioxane prepared as in Example 1 which was reacted with 0,0-diethyl dithiophosphoric acid following the procedure of Exampie 1, using, however, twice as much of the tetrachlorothioxane. This resulted in the production of a product analyzing: S, 25.2%; C1, 27.8%; P, 8.1%; calcd. S, 24.0%, Cl, 27.1%; P, 7.9%.

In insecticidal tests carried out as in Example 1, the trichlorothioxanemonothiol S-(0,0-diethyl phosphorodithioate) showed 100% kill against pea aphids using a 0.05% emulsion and 100% kill against two-spotted mites using a 0.1% emulsion.

Examples 3 and 4 The products of reaction of one mole of 0,0-dimethyl dithiophosphoric acid and of one mole of 0,0-diisopropyl dithiophosphoric acid with one mole of tetrachlorothioxane prepared in accordance with Example 1 were found to have only slightly less toxicity toward pea aphids than the product of Example 1.

Examples 5 and 6 The products of reaction of one mole of 0,0-dimethyl dithiophosphoric acid and of one mole of 0,0-diisopropyl dithiophosphoric acid with one mole of tetrachlorothioxane prepared as in Example 1 were found to have only slightly less toxicity toward pea aphids than the product of Example 1.

The organic dithiophosphate compounds of the formula 0 s 01 -F j! hai 012 4-n 2 L n s are those in which n is a number from 1 to 2 and each R is the same or a different organic radical such as a lower alkyl radical: methyl, ethyl, n-propyl, isopropyl, isobutyl, sec-butyl and n-butyl. In the above definition of the scope of the compounds of this invention, lower alkyl is defined to include those alkyl radicals of l4 carbon atoms.

The insecticidal activity of the products of this invention is greatest in those compounds of the general formula set forth above wherein R is methyl or ethyl and is greatest when the alkyl group has a low number of carbons. The optimum activity is also found in those compounds in which n equals 2.

In producing the compounds of this invention, the reaction between the tetrachlorothioxane and the ester of dithiophosphoric acid or its salt is carried out by heating the two reactants at a temperature at which reaction takes place but below the decomposition temperature in the range of 20 to 290 C., preferably in the range of 30 to 110 C. The reactants may be mixed in any desired order. in order to get complete reaction, it is preferable to use an excess over the theoretical amount of the ester of the dithiophosphoric acid. When the reaction is complete, the excess ester of the dithiophosphoric acid is readily removed by washing with water containing sufficient alkali to produce the water-soluble salt.

The reaction is preferably carried out in nonaqueous media. Organic solvents are desirable to aid in control of the reaction. Suitable solvents include benzene, toluene, xylene, ketones, anhydrous alcohol solvents and dioxane. It is preferable to use aromatic hydrocarbon or ketone solvents when using an amine salt of the dithiophosphoric acid ester or when using an amine or ammonia as a sequestering reagent. After the reaction is complete, the solvent is readily removed by distillation.

When the diester of dithiophosphoric acid is used as the free acid in the reaction with the tetrachlorothioxane, hydrogen halide which is liberated is preferably sequestered by adding a material to combine with the hydrogen halide as formed. it is convenient to use pyridine for this purpose. However, in its place, other tertiary organic amines may be used, and they may be added in equivalent amount at the beginning of the reaction or gradually during the course of the reaction. Likewise, the amine can be reacted with the diester of the dithiophosphoric acid prior to carrying out the reaction with the tetrachlorothioxane as in Example 1. Amines which can be used include pyridine, tertiary alkylamines such as trimethylamine, tributyl amine, triamylamine, dimethylaniline, and the like. inorganic bases may also be used. These include ammonia, alkali metal hydroxides, carbonates and bicarbonates, and alkaline earth metal hydroxides and carbonates.

As in the case of organic bases, the inorganic bases may also be used first to form a salt of the ester of the dithiophosphoric acid. When the salt of the ester of dithiophc-sphoric acid is used as the reactant, it is preferable to use a salt which is soluble in the organic solvent used for the reaction. The organic salts of amines are particularly satisfactory because of the good solubility of these salts in the nonreactive hydrocarbon solvents. When the free acid is reacted with the tetrachlorothioxane, the alkaline material is preferably added gradually as needed but it can be added all at once if desired. Ammonia is suitably added gradually as a gas, the solids are suitably added in finely divided form.

The dithiophosphoric acid ester is produced by reacting the lower aliphatic alcohol, which is to form a part of the ester, with P285, preferably in a nonreactive solvent such as benzene, toluene, xylene, hexane or cyclohexane, and removing the H28 which is liberated. The reaction is carried out at any temperature in the range of 50 to 120 (3., selecting tne lowest practical temperature without decomposition. If different radicals are desired for the various R radicals, a mixture of alcohols may be used in the production of the dithiophosphoric acid ester. Likewise, dithiophosphoric acid esters produced from different alcohols can be mixed for use in the reaction with the tetrachlorothioxane.

The methods by which the products of this invention are isolated will vary slightly with the reactants used and the product produced. in some instances, the chloside salt split out in the reaction separates and can be filtered off. in other instances, the chloride salt is best removed by washing with water. The excess salt of the ester of dithiophosphoric acid is also removed by the water wash. The benzene or other solvent is then removed by distillation leaving an insecticidally active residue. Further purification by selective solvent extraction or by adsorptive agents such as activated carbon, or clays, can precede the removal of the solvent. Likewise, an organic solvent can be added to aid in the purification by adsorptive agents. However, the product is generally satisfactory for use as a pesticide without further purification.

The compounds of this invention are used as the sole toxic agent in pesticidal formulations or in admixture with other toxicants for modification of the properties of the individual toxicants. They may be used, for example, in admixture with toxaphene, DDT, Thanite, chlordane, rotenone, pyrethrin, and the like, in many of the formulations suggested below.

The compounds of this invention are made into pesticidal compositions for use against insects and mites by dilution with an insecticidal adjuvant as a carrier therefor, by dispersing in an organic solvent, or in water, or by diluting with a solid insecticidal adjuvant as a carrier. Dispersions containing a surface-active dispersing agent have the advantage of spreading the toxic substance more effectively over the plant surface. Dispersions in organic solvents include dispersions in alcohols, pine oil, hydrocarbon solvents, difluorodichloromethane, and similar organic solvents. The compounds of this invention are also used in Aerosol formulations in which difluorodichloromethane and similar Aerosol propellants form the propellant vehicle.

Aqueous dispersions are made up from the compounds of this invention, a surface-active dispersing agent and water as the essential ingredients. The amount of the compounds of this invention in the aqueous dispersions when diluted for spraying of plants will be in the range of about 10.0% to about 0.000l% of the aqueous dispersion.

The acqueous dispersion will ordinarily be made up from a concentrate, and the concentrate will be dispersed in water to the proper concentration for application to the plants to be treated in the field. The concentrate is composed essentially of the compound of this invention and a surface-active dispersing agent. The concentrate may also contain sufficient amounts of organic solvents to aid in effective dispersion. The amount of surfaceactive dispersing agent used is usually at least 5% of the amount of toxic compound in the concentrate.

Suitable surface-active dispersing agents for use in the compositions of this invention are those disclosed in Chemistry of Insecticides, Fungicides and Herbicides (Donald E. H. Frear, Second Edition (1948), pages 280-287) for use with known insecticides and include neutral soaps of resin, alginic and fatty acids and alkali metals or alkylamines or ammonia, saponins, gelatins, milk, soluble casein, flour and soluble proteins thereof, sulfite lye, lignin pitch, sulfite liquor, long-chain fatty alcohols having 12-18 carbon atoms and alkali metal salts of the sulfates thereof, salts of sulfated fatty acids, salts of sulfonic acids, esters of long-chain fatty acids and polyhydric alcohols in which alcohol groups are free, clays such as fullers earth, China clay, kaolin, attapulgite, and bentonite and related hydrated aluminum silicates having the property of forming a colloidal gel. Among the other surface-active dispersing agents which are useful in the compositions of this invention are the omega-substituted polyethylene glycols of relatively longchain length, particularly those in which the omega substituent is aryl, alkyl, or acyl. Compositions of the toxic material and surface-active dispersing agent will, in some instances, have more than one surface-active dispersing agent for a particular type of utility, or in addition to a surface-active dispersing agent hydrocarbons such as kerosene and mineral oil will also be added as improvers. Thus, the toxic material may contain a clay as the sole adjuvant or clay and hydrocarbon, or clay and another surface-active dispersing agent to augment the dispersing action of the clay. Likewise, the toxic material may have water admixed therewith along with the surfaceactive dispersing agent, sufficient generally being used to form an emulsion. All of these compositions of toxic material and surface-active dispersing agents may contain in addition synergists and/or adhesive or sticking agents.

What I claim and desire to protect by Letters Patent is:

1. As a new composition of matter a compound of the formula o i. i 014- hSP-(OMzlfl in which n is a number from 1 to 2 and R is a lower alkyl radical.

2. As a new composition of matter a compound of the formula in which R is a lower alkyl radical.

3. As a new composition of matter a compound of the formula s ll C1 SP- OR r-E 3T 212 in which R is a lower alkyl radical.

4. As a new composition of matter a compound of the formula 0 i Clr E }SP(OC2H5)2 5. As a new composition of matter a compound of the formula 0 I. i Cir-E B W-(002E951 the formula 0 s ClaF 3-S Ii -(O CH3)2 12. A pesticidal composition comprising the compound of claim 11 and an insecticidal adjuvant.

13. As a new composition of matter-a compound of the formula O i CIQ-E j-SP(OCH(CHal2)z 14. A pesticidal composition comprising the compound of claim 13 and an insecticidal adjuvant.

15. As a new composition of matter a compound of the formula 0 i 012% j[SP-(OCH3)2] 2 16. A pesticidal composition comprising the compound of claim 15 and an insecticidal adjuvant.

References Cited in the file of this patent UNITED STATES PATENTS 2,725,331 Haubein Nov. 29, 1955 

1. AS A NEW COMPOSITION OF MATTER A COMPOUND OF THE FORMULA
 6. A PESTICIDAL COMPOSITION COMPRISING THE COMPOUND OF CLAIM 1 AND AN INSECTICIDAL ADJUVANT. 